Tear-Off Lid and Method For Its Manufacture

ABSTRACT

The invention relates to a lid ring ( 20′ ) for production of a tear-off lid, whereby a hot-sealing coating ( 62 ) is only applied to the edge ( 68 ) of the dispensing opening ( 25 ). A material saving is thus possible relative to conventional full-surface application. A coating different from the hot-sealing coating can form the lid ring surface outside the hot-sealing coating.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Swiss patent application No. 453/05, filed on Mar. 17, 2005, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

The invention relates to a tear-off lid comprising a lid ring with a take out opening covered by a tear-off foil and wherein lid ring and tear-off foil are releasable connected to each other by a hot sealable plastic coating in a connection area around the edge of the take out opening. Further the invention relates to a container with a tear-off lid. Still further the invention relates to a method for the manufacture of a tear-off lid wherein a tear-off foil is fixed by a hot sealable material to a ring shaped lid with a take out opening.

PRIOR ART

It is known to provide lids on containers in the form of cans or boxes, respectively, as ring shaped lids, in particular metal lids, being permanently fixed to the container and being provided with a take out opening in said lid which is closed by a tear-off foil, and in particular a tear-off metal foil, fixed to the ring shaped lid by hot sealing up to the first use of the contents of the package. Such lids are known as tear-off lids. An additional plastic cover that is arranged over the metal lid provides a closure for the package during the consumption time of the contents of the package. It is known to make the ring shaped lid from a starting material coated on its whole surface wherein a heat sealable coating of polypropylene or a coating containing polypropylene has been provided on the whole surface of the upper face of the starting material where the tear off foil will be hot sealed. This coating is subject to the manufacturing steps during forming of the ring shaped lid. From WO 01/07330 it is known to apply the hot sealable full surface coating of the ring shaped lid only after the forming thereof.

SUMMARY OF THE INVENTION

It is the object of the invention to improve a tear-off lid of the mentioned kind.

This object is met by a tear-off lid with the characterizing features of claim 1.

By limiting the hot sealable coating to the border of the take out opening or only to the connection area and thus essentially to the actual sealing area, it is possible to save a considerable amount of hot-sealing material. It has been found that the hot sealable coating material has disadvantages for the forming of the lid outside of the sealing area and for example is frequently damaged during flanging. Outside of the sealing area a different coating of the lid can be provided, for example a coating made of PET (polyethylene terephthalate) which is already known in the prior art as the coating on the lower face (thus as the coating facing the contents of the container). In this case the PET-coating may lie beneath the hot sealable coating within the connection area or the border of the take out opening, respectively, or may be omitted there. The hot sealable coating is preferably a polypropylene coating or a coating containing polypropylene, but other hot sealable substances can be used as well.

Another object of the invention is to provide a method for the manufacturing of tear-off lids.

This object is met for the method mentioned at the beginning with characterizing features of claim 9.

In special embodiments of the method the hot sealable coating is applied before applying and sealing of the foil only on the border or the connection area, respectively, on the one hand to the preformed or formed ring shaped lid or on the other hand to the not yet formed starting material on the areas that later form the border or the connection area, respectively.

In another embodiment the hot sealable coating is specifically applied as well to the preformed ring shaped lid on the special flange (so called “retort-curl”) of the edge of the take out opening.

In both embodiments the hot sealable coating can be applied to the bare metallic lid ring or on the bare metallic starting material (wherein the metal may be a metal with a metallic coating) or on the other hand the hot sealable coating can be applied to a lid ring that is already provided with a non metallic coating or on a starting material that is already provided with a non metallic coating and wherein said non metallic coating is not suitable for hot sealing and is for example a PET coating.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments, advantages and uses of the invention follow from the dependent claims and from the following description and the drawings, wherein:

FIG. 1 is a schematic side view of an apparatus for conveying and manufacturing lids;

FIGS. 2 to 8 show sectors of metal lids for the explanation of lid manufacture;

FIG. 9 shows another preferred embodiment of a conveying apparatus;

FIG. 10 shows the coating of starting material for the lid ring or for the tear-off foil with hot sealable material;

FIG. 11 shows the coating of a lid ring with hot sealable material;

FIG. 12 shows the coating of another embodiment of the lid ring with hot sealable material;

FIG. 13 shows a coated lid ring before applying the tear-off foil;

FIG. 14 shows a tear-off foil coated in its border area with hot sealable material; and

FIG. 15 shows a section of an embodiment of a tear-off lid.

WAYS OF IMPLEMENTING THE INVENTION

Known methods and apparatus for making metal lids with tear-off foils are shown in prior art FIGS. 1 and 9, respectively. FIGS. 2 to 8 show the result of manufacturing steps during manufacture of such covers or lids, respectively. FIG. 1 shows a schematic side view of an apparatus 1 which is provided with several working stations 3 to 8 and a further station 9 arranged on a machine frame 2. A conveyor 10, 13, 14 conveys lid parts and finished lids with tear-off foil in conveying direction shown by arrow C from the starting point at the staple 11 to the end of the apparatus where the objects move by chutes into trays 16 or 17. The objects are taken from the staple 11 in a known manner and enter into the conveyor. The conveyor is provided with two long rails 10 each arranged on one side of the lid parts or lids, respectively. By lifting the rails 10 in direction A by a crank drive 14, the lid parts or lids, respectively, lying within the work stations 3 to 9 and in rests 10′ between the work stations are lifted and are then displaced by an amount in forward direction shown by arrow B (directed in same direction as arrow C) by a crank drive 13 moving the rails in forward direction B. The rails are then moved downwards in direction of arrow A and the lid parts or lids, respectively, are again placed on the rests. The rails 10 are then moved below the rests and in backward direction of arrow B and thus in opposite direction to arrow C and then make the same conveying movement again. Between the conveying movements the lid parts or lids, respectively, lie on the rests in the working stations and in rests in between and the lid parts or lids, respectively, are stationary within the working stations and are worked upon therein. After all work stations have finished their working operation another transport cycle takes place. FIG. 2 shows stapled metal blanks 20 as an example for the lid parts of the staple 11. These blanks are for example round metal disks. As an example their diameter is 11 centimetres. Other basic shapes are of course possible, such as square or rectangular shapes. Of course other diameters can be selected. The blanks have already been preformed at their edges as shown in FIG. 2 by means of another machine. According to one embodiment of the present invention they may be coated by a hot sealable material in an area only or they will be coated according to another embodiment in a further step in this area only. Both embodiments will be explained later. Only a sector of each disk-shaped blank is shown in FIG. 2 and as well in the following Figures to simplify the drawings. In the first working station 3 of FIG. 1 the blanks are worked upon with an upper and a lower die to punch an opening (take out opening of the lid) into the disk, as can be seen in FIG. 3 in which the edge of the opening is referenced as 21 and the punched out round plate is shown as 27. This plate is moved as scrap into bin 12 of FIG. 1. The punching working station 3 is operated by a drive 15 as it is the case as well for the following working stations. In working station 4 the edge 21 is drawn downwardly resulting in the shape 22 of the edge shown in FIG. 3. The now ring shaped lid parts or lid rings 20′ respectively, are then conveyed into working station 5 wherein a foil 25 is placed over the opening of lid ring 20′ and is fixed to the surface thereof by heat sealing, as can by seen in FIGS. 5 and 6. The underside of the metal foil may be provided to this end according to the state of the art with full surface coating of a plastic layer suitable for heat-sealing. The foil cut 25 that is needed is usually punched out within station 5 from a broad sheet of foil and placed over the middle opening of the annular disk and in the heat sealing station the foil is pressed to the edge of the round opening of part 20 and heat is used, so that the foil 25 is fixed and sealed to the lid ring 20′ by melting and then cooling down of the plastic layer. This is known to the person skilled in the art and is not explained in greater detail. A cooling station 7 may be provided for cooling down. In working station 8 an embossing step will provide the foil 25 with an embossment 24 (FIG. 7) and the edge 22 will beaded further to form the finished edge 23. The finished lids 20 are tested in a testing station 9 which comprises usually a test of air tightness for the tear-off foil 25 fixed to the lid. If the foil is fixed to the metal ring in an airtight manner the lid is conveyed to the bin 16 for the finished lids. If the tested lid is not airtight it will be moved by the other shown chute into scrap bin 17.

FIG. 13 shows an embodiment of a ring shaped lid for a tear-off lid according to the present invention. The lid ring 20′ can be shaped similarly or identical to the lid rings or tear-off lids, respectively, shown in FIGS. 2 to 8. In FIG. 13 the lid ring is fully shown and as well its take out opening 25′ which is later covered by the tear-off foil 25 by sealing this foil on the lid ring. Contrary to the state of the art and according to the invention the hot sealable coating is provided only on the border of the take out opening and in particular only in the actual connection area of ring lid and tear-off foil, which is shown in FIG. 13 by a strip 62 consisting of hot sealable plastic material. Outside of the border of the take out opening (or of the inner border of the lid ring, respectively) and in particular outside of the actual connection area, there is, according to the invention, no hot sealable plastic coating provided. Thus the remaining surface of the lid ring 20′, that means the surface being outside of the border and in particular outside of the connection area and in particular the surface formed for fixing to the container or the outer border of the lid ring, respectively, is not provided with a plastic coating, or if the case may be, only with a plastic coating different than the hot sealable plastic coating. The hot sealable plastic coating is in particular a polypropylene layer or a layer containing polypropylene, for example a lacquer layer containing such particles. Such hot sealable coating materials are known in the prior art and are commercially used for hot sealing of tear-off foils. A plastic coating different therefrom, and which thus forms the sole plastic coating outside of the border of the take out opening or connection area, respectively, may be a coating consisting of PET (polyethylene terephthalate). Such a coating not suitable for heat sealing may be present as well on the border or in the connecting area, respectively, but is then situated beneath the heat sealable coating 62. The other side of the lid ring that is not visible in FIG. 13 can be coated as well with such a coating different than the heat sealable coating which can as well be a PET-coating.

FIG. 10 shows an alternative manufacturing wherein the coating material suitable for heat sealing is applied to the starting material for the manufacture of the lid rings. The starting material 60 is a metal blank, which may be provided with a metallic coating. On this metal blank a plastic coating that is not suitable for heat sealing may be provided, which is for example the PET-coating mentioned above. This coating can be provided on both sides of the metal blank 60, so for example on the whole upper surface visible in the Figure and/or as well on the lower surface that is not visible in the Figure. On this starting material 60 the heat sealable plastic coating, in particular the polypropylene coating, is applied such that it will be situated on the lid blank 20 and lid ring 20′, respectively, made from the starting material 60 on the border of the take out opening 25′ or in the connection area, respectively. This is shown in FIG. 10 again by the strip like plastic coating 62, which for example can be applied by spraying with movable nozzles 61 or can be applied as a finished band. After the application of the heat sealable plastic coating, making of the lid blank 20 takes place and then the making of the lid ring 20′ and of the finished lid according to FIGS. 2 to 8. The fixing of the tear-off foil by heat sealing is done in the generally known manner.

FIGS. 11 and 12 show other embodiments for the application of the heat sealable coating and the making of the ring lid, respectively. In this embodiment the heat sealable coating 62 is applied to the preformed lid ring 20′ on which the take out opening has been made and the edge of the take out opening has been beaded. In the alternative of FIG. 11 this is a simple flange 66 but in the alternative of FIG. 12 this is a special flange known in the art as “retort curl”. The cut edge resulting from the making of the take out opening, where a coating, if any, of the blank is no longer intact, is beaded upwardly and inwardly by this kind of flanging 67 as can be seen in FIG. 12. For both alternatives the heat sealable coating 62 is applied to the border 68 of the take out opening, for example by a nozzle 63 which is stationary over the rotating lid ring or which moves along the border of the stationary lid ring. In the variant of FIG. 12 with the retort curl 67 it is preferred that the coating 62 covers the flange, so that the cut edge is as well enclosed by the coating.

As already explained the coating may cover on the one hand the whole border 68 of the take out opening as shown with coating 62 of FIG. 12 or on the other hand the coating may be applied with less width so that it covers essentially only the connection area on which the tear-off foil is fixed. As explained above an additional plastic coating that is not suited for heat sealing can be provided on the lid ring, for example a PET-coating, which covers the lid ring on those areas not covered by the heat sealable coating 62. Relevant for the invention is in any case that the heat sealable coating 62 does not extend over the whole upper surface of the ring shaped lid as has been the case in the prior art. The lower surface of the ring shaped lid can be covered by a coating not able to be heat sealed, preferably again a PET-coating. The formed outer border 64 for connecting the finished lid to a container in generally known manner can be made in different known ways and is not explained here in detail.

FIG. 15 shows the embodiment of FIG. 12 with already fixed tear-off foil 25. Same reference numerals stand for the same elements so in particular the heat sealable coating 62 which extends over the retort curl 67. It is shown as well in FIG. 15 that the heat sealable coating 62 at the border of the take out opening may extend as well over the actual connection area of tear-off foil and border 68 which is shown by part 62′ of the heat sealable coating which extends a little bit over the connection area and is present on the border 68 outside of the connection area. The surface 70 of the lid with the lid ring 20′ may be provided with a coating and in particular a PET coating as already mentioned several times, which may extend as well under the heat sealable coating 62 on the border 68. The lower side 69 can be provided with such a coating or with another plastic coating, which is preferably provided already on the flat starting material. The heat sealable coating 62 may be put on as a finished band instead of applied by nozzles 63 in the embodiments of FIGS. 11, 12 and 15 as well.

Further FIG. 14 shows an embodiment in which a heat sealable coating has been applied on the lower side of the tear-off foil 25 in form of a coating 65 only on the border thereof, in particular as a strip shaped coating 65. This coating can be applied instead of or additionally to the heat sealable coating 62 of the lid ring and leads in the established connection of FIG. 15 essentially to the same result in which the heat sealable coating 62 is present only on the border 68 or within the connection area of lid ring and tear-off foil. Here as well the width of coating 65 can be selected such that a retort curl 67 is covered. Both coatings 62 on the ring lid and 65 on the tear-off foil can be present. The application of the coating 65 to the lower surface of the tear-off foil can be done according to FIG. 10, wherein in this case the starting material 60 is the tear-off foil material which tear-off foil is later punched out with the tear-off flap 71 from the starting material 60.

FIG. 9 shows a conveying apparatus 30 according to a preferred embodiment in perspective view. This conveying apparatus is adapted for conveying lid shaped objects of the described kind. The conveying apparatus serves as well for the step by step conveying of the lid parts and lids, respectively, towards each of the working stations, which are preferably the working stations for the manufacture of lids and the testing station 9. These stations are not shown in FIG. 9 but it is known to the man skilled in the art how to arrange these stations along the conveying apparatus for performing the actual working. In FIG. 9 it is further shown that an additional conveying apparatus 30′ can be arranged adjacent the conveying apparatus 30, which may be driven by the same drive 33, 37 or may comprise its own drive. Additional conveying means may be provided to increase the total number of conveyed lid parts or lids, respectively. With the shown conveying apparatus 30 lid parts and lids, respectively, can be conveyed with a high rate of for example 200 parts per minute and with reproducible steps between the stations. If further results a flexible concept for a large range of the format of the objects or lids, respectively, which may range for example for round lids from a diameter of 50 to 200 mm and may take up as well different rectangular formats for example for the current fish cans. The conveying apparatus is further designed as a compact module for one track or multi track arrangement as shown.

In the shown preferred embodiment the conveying apparatus comprises two toothed belts 31 and 32, in particular lying with their surfaces in the same planes and thus running coplanar and being led over pulleys 34, 36 at the beginning and end of the conveying apparatus so that an endless toothed belt drive in the necessary length for the number of working stations is provided. A step motor or a servo motor driving the belts by toothed rollers, as can be seen in the Figure with motor 33 and driving axle 38, provides the stepwise toothed belt movement synchronized with the working stations. If further conveying apparatus, as apparatus 30′ are provided, their toothed belts can be driven by the same motor over additional driving axles or they may be provided with their own motor drive. Motor 33 is controlled by a control 37 for making the step by step forward movement which control 37 may be a common control for the lid making apparatus, which controls as well the working stations and the station 9, or which control 37 is a control for the conveying apparatus only which is in communication with a master control for the lid making. Motor 33 and the other drive components for the toothed belts are arranged on a machine bed 35 of which only feet 35 are shown. Dogs are connected to the toothed belts which are depicted in FIG. 9 generally with 40 and wherein dogs lying opposite each other on toothed belts 31, 32 form an uptake for each object. The uptake formed by the dogs 40 is moved along the conveying path and in direction of shown arrow C from the input side of the conveying apparatus which is at the motor position to the output side at the pulley 36 by the movement of the belts. A cover 50 over the toothed belt and the dogs is provided in the shown embodiment, which covers the belt and a part of the dogs. At the position of the working stations this cover 50 is provided with a recess 52 which allows taking off the objects from the dogs 40 so that the object can be taken away from the dogs, worked upon in the working station and then be put back again. Between stations there are generally provided no recesses 52 so that there the take off of objects from the dogs is blocked by cover 50. Additionally or alternatively to the blocking by cover 50 the dogs can be magnetic which may prevent a take off of the object during the conveying step as well if the object is made of a material that can be held by a magnet.

It is preferred that the distance between the toothed belts 31 and 32 can be set whereby the distance of opposing dogs 40 of the toothed belts can be adjusted to adapt the conveying apparatus to different object sizes. To this end transverse links 58 are provided which allow a simple setting of the distance between the toothed belts. The drive axle 38 is adapted to allow such a distance setting. The distances between dogs 40 on each toothed belt are given by the spacing of the teeth of the toothed belt and the fixation of the dogs. This distance can preferably be changed to adapt to the object size by changing the toothed belts to another set of toothed belts having dogs with a different distance to each other. In this way the preferred take up size can be provided by setting the distance between the toothed belts and changing to toothed belts with different distances between the dogs. Thereby a changeover to different object sizes can be done for all dogs at the same time and quickly. The manufacturing steps described for the tear-off lids and the corresponding working stations and conveying apparatus are to be understood as examples only and serve for the understanding of the invention. The invention can be practiced as well for tear-off lids manufactured in a different way.

For both embodiments described of the manufacturing and conveying apparatus, respectively, wherein the heat sealable coating is applied to the lid ring, it is necessary to provide a corresponding working station along the conveying path and of course ahead of the heat sealing station. For those embodiments where the coating is applied to the starting material, the coating is already present on the lid blanks at the beginning of the shown manufacturing and conveying paths, respectively, and as well on the material of the tear-off foil that only needs punching.

While there are shown and described presently preferred embodiments of the invention, it is to be understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. 

1. Tear-off lid having a lid ring (20′) with a take out opening (25) covered by a tear-off foil (25″), wherein said lid ring and said tear-off foil are releasable connected to each other with a heat sealable coating (62) along the border (68) of said take out opening by a connection area, characterized in that said lid ring is not coated or is coated with a plastic coating different from said heat sealable coating (62) outside of said border or said connection area.
 2. Tear-off lid according to claim 1, characterized in that the heat sealable plastic coating is a polypropylene coating or a coating containing polypropylene, and in particular a polypropylene containing lacquer coating.
 3. Tear-off lid according to claim 1, characterized in that the plastic coating different from the heat sealable coating is a polyethylene terephthalate coating or a coating containing polyethylene terephthalate.
 4. Tear-off lid according to claim 1 characterized in that the plastic coating different than the heat sealable coating extends on one side or on both sides over the whole lid ring and therefore lies in the connection area beneath the heat sealable coating.
 5. Tear-off lid according to claim 1, characterized in that the lid ring comprises a flanged edge (67) beaded towards the take out opening (25′) and that the flange is covered by the heat sealable coating.
 6. Tear-off lid according to claim 1, characterized in that the lid ring is made of metal.
 7. Tear-off lid according to claim 1, characterized in that the lid ring or the take out opening is round or oval or rectangular or is provided with another non round shape.
 8. Container with a tear-off lid according to claim
 1. 9. A method for manufacturing a tear-off lid wherein a tear-off foil (25) is connected to a lid ring (20′) with a take out opening (25) by heat sealing of a heat sealable material, characterized in that the heat sealable material (62) is applied on the lid ring only to the border (68) of the take out opening (25) or in the connection area with the tear-off foil and/or that the heat sealable material (65) is applied only to the border of the tear-off foil.
 10. Method according to claim 9 characterized in that the heat sealable material (62, 65) is applied on the starting material (60) before a forming or punching thereof.
 11. Method according to claim 9 characterized in that the heat sealable material (62, 65) is applied after a forming of the lid blank (20) or lid ring (20′) or after a punching of the tear-off foil.
 12. Method according to claim 9, characterized in that the heat sealable material is applied in liquid form or is laid on as a solid band.
 13. Method according to claim 9, characterized in that the lid ring (20′) is provided with a flange directed upwardly and inwardly (67; retort curl) and that the heat sealable coating is applied so that the flange is at least partly covered.
 14. Method according to claim 9, characterized in that the lid ring or its starting material, respectively, is provided at least on one side and preferably on both sides with a plastic coating that is not suitable for heat sealing.
 15. Method according to claim 14, characterized in that the coating not suitable for heat sealing extends beneath the heat sealable coating (62) by applying the latter as a layer on the coating not suitable for heat sealing.
 16. Method according to claim 9, characterized in that the lids are conveyed on a linear conveying apparatus by toothed belts or by chains to the working stations and in particular to the heat sealing station, as the case may be with a preceding working station along the conveying path wherein the heat sealable coating is applied to the lid rings following each other. 